Soft x-ray spectra from laser plasma effectively heated by a pulse train laser

Considerable progress has been made in the development of soft x-ray laser since 19851-2). Until now a powerful laser of single or double pulses has often been used to produce high density plasma. Recently we observed ASE (amplified spontaneous emission) in some lines of Al X and Al XI in a recombining plasma produced by a very low power laser of only 2 J which was composed of a train of many low power pulses separated by about 350 picosecond3). To understand more clearly the effect of multipulse irradiation on the production of laser plasma and x-ray emissions including ASE, in this paper we constructed a pulse train forming system and investigated the emitted soft x-ray spectra for various pulse trains. Our final goal is to develop a table top x-ray laser in the water window wavelength.